Algorithm for finding the winner (tic-tac-toe)?

Question

JavaScript

Tell me the most effective algorithm for finding the winner in tic-tac-toe.
This is what I got myself:

function checkWinner(arr) {
  let a = 0, b = 0, c = 0;
  for (let i = 0; i < 3; i++) {
    for (let j = 0; j < 3; j++) {
      if (arr[i][j] == 1) a++;
      if (arr[i][j] == 2) a--;
      if (arr[j][i] == 1) b++;
      if (arr[j][i] == 2) b--;
      if (i == 0 && arr[j][j] == 1 || i == 2 && arr[j][i - j] == 1) c++;
      if (i == 0 && arr[j][j] == 2 || i == 2 && arr[j][i - j] == 2) c--;
    }
    if (a == 3 || b == 3 || c == 3) return 1;
    if (a == -3 || b == -3 || c == -3) return 2;
    a = 0;
    b = 0;
    c = 0;
  }
  return /0/.test(arr.join('')) ? -1 : 0;
}

checkWinner();

But something I'm not very happy with the result, in my opinion it looks terrible.

Answer 1

For any square dimension, the length of the matching characters is adjustable,
default is the length of the array

function checkWinner(arr, length) {
   length = length || arr.length;
   var winner = [
      arr.map(row=>row.join('')).join(' '),
      arr.map((_,v)=>arr.map(row=>row[v]).join('')).join(' '),
      arr.map((_,v)=>arr[v][v]).join(''),
      arr.map((_,v)=>arr[v][arr.length - v - 1]).join(''),
   ].join(' ').match('1'.repeat(length) + '|' + '2'.repeat(length));

   return +((winner || ['0'])[0][0]);
}

Answer 2

function checkWinner(arr) {
    function Eq(a, b, c) {
        return a != 0 && a == b && a == c;
    }
    for (let i = 0; i < 3; i++) {
        // check rows
        if (Eq(arr[0][i], arr[1][i], arr[2][i])) {
            return arr[0][i]
        }

        // check cols
        if (Eq(arr[i][0], arr[i][1], arr[i][2])) {
            return arr[i][0]
        }
    }

    // check diagonal
    if (Eq(arr[0][0], arr[1][1], arr[2][2])) {
        return arr[0][0]
    }

    if (Eq(arr[0][2], arr[1][1], arr[2][1])) {
        return arr[0][2]
    }

    return 0
}

OFFTOP: tic-tac-toe joke https://github.com/asweigart/my_first_tic_tac_toe

Answer 3

I would designate the first player as a one, and the second as a four.
If the sum in a row, column or diagonal is 3 - the first one won, if it is 12 - the second one won.

Answer 4

https://codepen.io/FrontCoder/pen/vZBqjV